1. Field of the Invention
The present invention relates to a synthetic peptide and its use in an immunoassay for the detection of Equine Infectious Anemia (EIA) viral infection.
2. Description of the Prior Art
Equine Infectious Anemia is a viral disease, commonly known as swamp fever, which primarily affects horses and ponies. There is no known cure for the disease. Diagnosis and isolation is the only way to control the disease.
The accepted way to diagnose the presence of EIA has been to detect the presence of antibodies specific for the disease in the serum of affected animals using the Coggins or agar gel diffusion test described in U.S. Pat. No. 3,929,982 and U.S. Pat. No. 3,932,601. In the Coggins test, a prepared antigen is placed alongside the serum to be tested in an agar or gel medium. If EIA antibodies are present in the test serum, they will diffuse toward the antigen forming a precipitin line in the agar medium where they eventually meet.
This methodology is inherently insensitive in that the EIA antigen may be contaminated with non-EIA antigens during its preparation. Antibodies against non-EIA antigens may be present in the test serum and can react with the non-EIA antigens forming a variety of nonspecific precipitin lines. Even if the prepared EIA viral antigen can be purified, the Coggins test is labor intensive and demanding of considerable expertise in interpretation of results. The Coggins test procedure is also slow to yield results; it takes twenty-four to forty-eight hours for the formation of clearly visible precipitin lines.
Porter, U.S. Pat. No. 4,806,467, discloses a method for detecting the EIA virus using a competitive enzyme-linked immunoabsorbent assay incorporating a purified viral antigen and a monoclonal antibody. To obtain antigen, the EIA virus must first be cultured. The antigen is the p26 core protein of the EIA virus and is obtained through (purification of the cultured virus by a variety of means well known in the art. Immunizing mice with the antigen will produce hybridomas which will produce the monoclonal antibody specific to the p26 core antigen. The technique of culturing a virus increases the likelihood that the assay will yield false positive results since the virus may be contaminated with other forms of protein. Additionally, the EIA virus is hard to culture, making the Porter approach difficult for large scale production.
The use of a synthetic peptide in an enzyme linked (immunosorbent assay for the detection of human immunodeficiency virus (HIV) is disclosed in Shoeman, R. L. et al., Analytical Biochemistry 161:370-379 (1987). HIV and the EIA virus are members of the retrovirus family but have dissimilar structures and distinct amino acid sequences.
It is an object of the present invention to provide an assay for the detection of the equine infectious anemia virus which may be easily and quickly performed utilizing stable reagents which may be produced in sufficient amounts at a low cost. It is a further object of this invention to provide a pure source of antigen for use in such an assay to ensure accurate results.